1. Technical Field
The invention concerns an apparatus for automatic lubricant delivery, comprising a piston arranged in a cylinder, and a drive means connected thereto.
2. Description of the Prior Art
Such an apparatus is known from German patent specification No 43 21 452 or DE-U-92 14 096. While German patent specification No 43 21 452 proposes a construction in which lubricant is directly pressed out of the cylinder by means of a pressure piston and therefore the lubricant is disposed directly in the cylinder itself, the construction of DE-U-92 14 096 proposes fitting a lubricant pack or cartridge into the cylinder and expelling it by means of a piston. The two known constructions suffer from a number of disadvantages. Thus the disadvantage of the construction disclosed in German patent specification No 43 21 452 is in particular that, when the lubricant is urged out of the cylinder, the piston is subjected to very different loadings because of its geometrical shape and has a tendency to tip away slightly at the outer edge which is opposite the inside wall surface of the cylinder, or to form a gap between the piston and the inside wall surface of the cylinder, through which gap lubricant can pass into the region of the drive. The measures proposed in that publication for sealing the gap between the piston and the inside wall surface of the cylinder are at any event completely inadequate. Furthermore the lubricant dispenser is only activated by setting the dispensing time with a graduation at the desired time intervals, by electronic control, which is disadvantageous in particular when the lubricant dispenser is disposed at locations which are only accessible with difficulty and which scarcely permit setting of the dispensing time. Furthermore the design configuration of the means for setting the dispensing time in the apparatus is not very economical by virtue of the frequent one-off use thereof.
In the lubricant dispenser known from DE-U-92 14 096.3, admittedly no sealing problem is involved by virtue of the lubricant being disposed in a lubricant pack or cartridge, but the lubricant pack of cartridge cannot be completely emptied as the piston is of a stepped configuration in cross-section and the lubricant pack or cartridge cannot in principle be entirely emptied. Thus residues always remain behind in the lubricant pack or cartridge so that this arrangement only affords less than optimum utilization of the entire amount of lubricant in the lubricant pack or cartridge. Furthermore, in the case of the known lubricant dispenser, it is possible for them to give rise to explosions under adverse environmental conditions.
The object of the present invention, in an apparatus for automatic lubricant delivery, comprising a piston disposed in a cylinder and a drive connected thereto, is to avoid the disadvantages from which the state of the art suffers.
In accordance with the invention that is achieved with an apparatus for automatic lubricant delivery, as set forth in claim 1. Advantageous developments of the invention are recited in the appendant claims.
It is highly advantageous if the apparatus according to the invention has an on switch or circuit closer switch which is protected in relation to spray or splash water and which complies with international standard ID 65. Spray water protection is achieved by a suitable sealing arrangement for the on switch, whereby at the same time the entire apparatus for automatic lubricant delivery is protected against explosion. After activation of the on switch, the apparatus can only be switched off by cutting off the power supply. The preferred relinquishment of a switch-off function does not cause any problems because the automatic lubricant dispenser virtually never has to be switched off, but, by virtue of a preset lubricant delivery amount per day or other unit of time, remains in operation until all lubricant has been discharged from the cylinder.
The on switch or circuit closer switch is preferably in the form of a cylindrical pin co-operating with a contact means which is in the form of a spring contact disc. The spring contact disc is disposed on a board together with the other electrical components for controlling the discharge of lubricant. The spring contact disc is of a cup-like convex cross-sectional shape as long as the apparatus is not yet activated. Disposed opposite the spring contact disc is the on switch which is disposed in an opening in the wall of the housing of the apparatus. When the on switch which is in the form of an activation pin is pressed into the housing the front part of the activation pin or the on switch pushes the convex shape of the spring contact disc into a concave shape and the contact disc which is bent in that way and which is electrically conducting simultaneously touches two contacts which are arranged below the contact disc and by which the apparatus is started when contact occurs.
Preferably the activation pin has two projections which extend therearound and which are disposed at a spacing relative to each other corresponding to the wall thickness of the housing. In the non-activated condition one of the projections is disposed on the outside of the housing and the other projection is disposed on the inside of the housing. Upon activation, the projection disposed on the outside of the housing is pushed through the opening in the housing until the projection which previously was on the outside of the housing is on the inside and prevents the activation pin from moving back out of the housing. Sealing means disposed beneath the head of the activation pin bear against the housing on the outside thereof after the activation pin has been pushed in, and seal off the interior of the housing relative to the outside thereof. A further sealing action for the housing is achieved by the projection which bears at the inside against the inside wall surface of the housing.
Preferably the on switch is arranged in a depression in the housing of the apparatus and upon activation therefore does not project beyond the outside periphery of the lubricant dispenser.
The invention is also based on the realization that a piston of a shape which is convex in cross-section is very easy to produce and also does not have any tendency in the edge region to open up a gap between the piston and the cylinder. In particular however by virtue of the line guidance of the piston which is of a convex cross-section, a sealing body can preferably be accommodated in a onepiece sealing lip which in the event of high pressure in the cylinder is automatically pressed against the inside wall surface of the cylinder and the edge of the piston and thus provides for a very good sealing effect.
The fact that the cylinder head is adapted to the convex shape of the piston also ensures that the lubricant can be entirely discharged from the apparatus.
It is also desirable if the apparatus has a microprocessor and a memory connected thereto and the apparatus can be preset by way of those means for a predetermined quantitative discharge of lubricant per unit of time which can only still be triggered off by the on switch.
For the purposes of observing emptying of the apparatus according to the invention the cylinder wall is at least partially of a transparent material so that the silhouette of the piston or the sealing body can be seen from the exterior. In addition, a scale in the form of alphanumeric or abstract characters is provided along the main axis of the cylinder so that it is possible to provide an accurate assessment about the emptying of the lubricant from the cylinder. Such a display device is very simple to produce and to read off and is also highly accurate. It is precisely if the cylinder wall is of plastic material that the transparency or translucency of the entire cylinder wall can be very easily achieved.
For the sake of improved reading-off, it is desirable if the upper edge of the piston or the sealing body is provided with a clearly visible color, for example a signal color.
It may be desirable for the apparatus to be switched over from the winter mode of operation to the summer mode of operation and to store corresponding quantity/time presettings in a non-volatile memory. The change-over switching action can be triggered off by means of a further switch. That provides for optimum lubricant supply by adaptation to the usual external temperatures in the winter time and the summer time respectively.
The drive means for the automatic lubricant dispenser can be an electrical dc or ac motor, as is frequently used as such in electrical engineering.
It is however particularly advantageous to use a stepping motor which drives the piston within the cylinder of the lubricant dispenser.
The advantage here is in particular that a stepping motor can be better controlled for the purpose according to the invention because, in dependence on electrical signals, for example a number of electrical pulses, it reacts with degree accuracy and thus with less dependency on temperature influence than is the case with for example dc motors. The use of a stepping motor thus permits overall simpler actuation of the drive by a control board which in particular has a pulse counting device and a device which controls the stepping distance of the motor in dependence on the electrical pulses applied. In that way the stepping motor can also be switched off when it has pressed the piston into the delivery region of the cylinder. That is achieved by a number of stepping motor control pulses being preset in a memory and the stepping motor or the lubricant dispenser being switched off as soon as that number is attained. The device for switching off the stepping motor thus comprises a comparator or a control unit having a comparison program which compares the number of pulses already set with the stored maximum pulse number and in dependence thereon transmits a control signal to the stepping motor and enables a further movement of the stepping motor by a predetermined number of steps or switches off the stepping motor.
The pulse generation device can be a pulse/control signal generator which generates pulses in dependence on time, for example ten pulses per day, or in dependence on the requirement of the machine unit to be lubricated, so that in a mode of operation which is independent of a machine, the stepping motor and therewith the piston performs a given stepwise deflection within a given unit of time while in the case of actuation which is linked to a machine the pulse generator produces the necessary number of pulses on demand.